| The terahertz (THz, 1012 Hz) wave, located between millimeter wave and far infrared wave, with the frequency between 0.1 THz and 10THz, belongs to far-infrared band (the wavelengths between 30um to 3mm). The Terahertz time domain spectroscopy develops the linear spectrum from 100GHz to 1THz frequency region. One can analyze and understand the physical properties of matter by the THz detection.In general, the metal screens the electromagnetic wave. The metal plate can not transmit the electromagnetic wave when its lateral size is larger than the corresponding wavelength. Recently, the enhanced special transmission phenomena from the metal structures were found at some special frequencies. In this thesis, THz spectroscopic properties of the metal sub-wavelength structures are studied.The silicon is a standard semi-conductor material. It acts as a foundation stone of the information age, which plays an important role in the field of material science. We firstly measured the transmission properties of different doped silicon wafers and studied its optical characteristics in THz frequency range. Some optical parameters of silicon in the THz frequency range are obtained, which provide the basic data for the further study of THz transmission properties of metal fractal structures based on the silicon as substrate.The main work of this thesis is presented by studying of THz transmission properties of sub-wavelength metal fractal structures. We measured the terahertz transmission of metal fractal slits on copper foil and on the substrate of silicon by using THz time-domain spectroscopy (THz-TDS) system. The laws of THz transmission of fractal structure are investigated, which have the prospect of potential application in the field of THz photonic devices. We attribute the high transmittance from metal sub-wavelength structures to geometric resonances. |
PDF Full Text Request